Heretofore, there have been proposed various mobile broadcasting systems or mobile communication systems for providing mobile bodies with information through wireless links (Patent Document 1, Patent Document 2).
For example, Patent Document 1 discloses a vehicle broadcast reception system for re-receiving a broadcast if a running vehicle has failed to receive the broadcast while the vehicle was passing through a poor reception site, such as in a tunnel or below an overhead line, even when the vehicle was positioned in the broadcasting area of a broadcasting station.
According to the technology disclosed in Patent Document 1, the positional information of the vehicle, which is acquired by a GPS receiver or the like mounted on the vehicle, is continuously transmitted from the vehicle to an information center. The information center, which stores continuous broadcast data in its memory, searches its own map database based on the received positional information of the vehicle, and identifies a poor reception site and a poor reception time. Then, the information center reads information broadcast at the poor reception time, for examples, compresses the read information, and transmits the compressed information to the vehicle. The vehicle receives the transmitted information, so as to allow the vehicle occupants to view a broadcast that could not be received at a poor reception site, such as in a tunnel.
However, the disclosed technology is disadvantageous in that the information center is required to have a poor reception site database, as well as a predictor and a decision unit for identifying poor reception sites and poor reception times. Further, it is highly costly to construct the information center through the generation of the poor reception site database, the development of programs for the predictor and the decision unit, etc.
In order to solve the above problems, an information communication system disclosed in Patent Document 2 is capable of subsequently setting a data supply time when a vehicle is unable to receive data, such as when the vehicle is not in use or when a vehicle-mounted communication device is switched off, and requesting an information center to retransmit the data to acquire the non-acquired data.
The technology disclosed in Patent Document 2 is problematic since in order to set the data supply time, the data of a next scheduled updating time must be included within the data transmitted from the information center, and the frame structure of the transmitted data is limited to a certain structure.
Patent Document 1: Japanese Laid-Open Patent Publication No. 11-68686 (FIG. 2).
Patent Document 2: Japanese Laid-Open Patent Publication No. 11-154973 (FIG. 3).